In recent years, a portable terminal has been provided with a wireless charging function for wirelessly charging a built-in battery, and this wireless charging is carried out by a wireless power reception module that is built in the portable terminal and a wireless power transmission module that supplies power to the wireless power reception module.
In addition, the wireless charging may be classified into a magnetic induction type and a magnetic resonance type, and also classified into a PMA wireless charging method and a Qi wireless charging method according to a method of detecting an approach of the wireless power reception module to the wireless power transmission module.
The PMA wireless charging method controls an operation of the wireless power transmission module by detecting the approach of the wireless power reception module using a permanent magnet and a hall sensor, and the concept of this is schematically shown in FIG. 1.
As shown in FIG. 1, a permanent magnet 14 and a hall sensor 12 are installed in a wireless power transmission module 10, and a magnetic substance so-called attractor 22 is installed at approximately the center portion of a wireless power reception module 20.
When the wireless power reception module 20 approaches the wireless power transmission module 10, a magnetic force line is generated from the permanent magnet 14, a difference of a voltage value in the hall sensor 12 is generated while a partial path of the magnetic force line is changed by the attractor 22, and when the difference of the voltage value exceeds a certain level, it is recognized that the wireless power reception module 20 approaches the wireless power transmission module 10, and the wireless power transmission module 10 is operated so that wireless charging is performed.
Meanwhile, in recent years, the thickness of the wireless power reception module 20 built in a portable terminal has been also reduced along with reductions in the weight, thickness and size of the portable terminal, and a problem that the thickness of the wireless power reception module 20 should be designed to be, for example, 0.5 mm or less or even 0.3 mm or less is generated. In this manner, when the thickness of the wireless power reception module is designed to be 0.5 mm or less or even 0.3 mm or less, it is difficult to increase the thickness of the attractor 22 to a predetermined thickness or more.
In addition, the attractor does not have a problem in exercising a function of detecting the difference of the operating voltage value in the hall sensor to be a predetermined value or more by changing the path of the magnetic force line of the permanent magnet 14, as the thickness or area of the attractor is increased, but cannot increase its size and thickness due to the limitations in the structure and shape of the wireless power reception module.
For example, when the attractor is configured to have a thickness of 200 μm or less, this has the following problem.
That is, in the PMA wireless charging method, the difference in the voltage value of the hall sensor should be detected to be approximately 50 mV (standard operating voltage value) or larger in order to detect the approach of the wireless power reception module. In addition, since it is difficult to accurately align the centers of the wireless power transmission and reception modules, it is necessary that the difference of the voltage value in the hall sensor should be detected as being approximately 50 mV or larger within a predetermined non-alignment region even when the centers of the wireless power transmission and reception modules are not aligned with each other.
However, when the attractor is configured to have a substantially small thickness, for example, 150 μm, the difference of the voltage value in the hall sensor is far below the standard operating voltage value (50 mV) in a state in which the centers of the wireless power transmission and reception modules are not aligned, and therefore the approach of the wireless power reception module is not detected so that wireless charging is not performed.
As an alternative to this, in Korean Patent Laid-Open Publication No. 10-2012-0100217, a technique for facilitating the alignment by disposing a fixing magnet and a fixing magnetic substance corresponding to each other respectively at sides of a charging receiver and a charging transmitter has been disclosed.
In addition, a plurality of sensing magnets in addition to the fixing magnetic substance are disposed at the charging receiver side, so that the hall sensor may detect a magnetic force of the sensing magnet even when the charging receiver is mounted at a different angle to the charging transmitter side.
However, in the above-described Patent, even when it is detected that the charging receiver is mounted at a different angle to the charging transmitter side through the plurality of sensing magnets, only mounting angles of the charging receiver and the charging transmitter are changed and the hall sensor is always located directly above the sensing magnet.
In other words, the hall sensor may detect the magnetic force of the sensing magnet only in an aligned state in which the hall sensor is located directly above the sensing magnet so that the charging transmitter may be operated, but when the hall sensor is located at a position other than a position directly above the sensing magnet, the charging transmitter may not be operated.
Meanwhile, the attractor is manufactured by a punching process, and the side surface of the attractor manufactured by the punching process constitutes a punched surface. At this time, when the attractor is made of a magnetic substance containing a metal component, when the punched surface is used for a product while it is exposed to the outside, the following problems are generated.
That is, when particles such as minute particles or powder particles are separated from the punched surface exposed to the outside, the particles separated from the punched surface also contain a metal component having conductivity, and therefore when the separated particles come into contact with an electronic circuit located around them, there arises a problem that the electronic circuit is shorted by the metal component.
In addition, in a salt water spray test process to test reliability of the attractor, a contact with moisture or the like on the punched surface that is an exposed surface may occur. Therefore, when penetration of moisture or the like into the punched surface occurs through the contact with moisture or the like, there also arises a problem that the exposed surface is oxidized.